PHILADELPHIA -- An 89-year-old Nazi war crimes suspect died in custody hours before a U.S. ruling Wednesday that he should be extradited to Germany to face trial.

Johann Breyer died Tuesday night at a Philadelphia hospital, where he had been transferred Saturday after a month in jail, his lawyer and the U.S. Marshals Service said. His death was disclosed Wednesday just as U.S. Magistrate Timothy Rice approved the extradition request, which would have needed final U.S. government review.

Rice found probable cause that Breyer was the person being sought by German authorities over his suspected service as an SS guard at Auschwitz during World War II.

"No statute of limitations offers a safe haven for murder," he wrote in his ruling.

U.S. marshals had arrested him in June outside his home in Philadelphia. He was facing charges of aiding in the killing of 216,000 Jewish men, women and children at a Nazi death camp.

"As outlined by Germany, a death camp guard such as Breyer could not have served at Auschwitz during the peak of the Nazi reign of terror in 1944 without knowing that hundreds of thousands of human beings were being brutally slaughtered in gas chambers and then burned on site," Rice wrote.

Breyer claimed he was unaware of the massive slaughter at Auschwitz and then that he did not participate in it, but "the German allegations belie his claims," the judge wrote.

Breyer's lawyer, Dennis Boyle, said Breyer's health had deteriorated but he didn't know the cause of death. Breyer's wife and survivors could not immediately be reached for comment.

German authorities in the Bavarian town of Weiden issued a warrant for Breyer's arrest in June 2013 under revised laws that allow Nazi guards to be charged with accessory to murder even without proof they took part in the killings, because the camps' sole function was to kill people.

The same legal strategy was used to charge and convict former U.S. autoworker John Demjanjuk on charges he served as a death camp guard at Sobibor in occupied Poland. Demjanjuk died in a Bavarian nursing home in 2012 while appealing his 2011 conviction.

The 2013 warrant accused Breyer of 158 counts of accessory to murder -- one count for each trainload of victims brought to the Auschwitz death camp in occupied Poland from May to October 1944, when Breyer was allegedly a guard there.

Breyer told The Associated Press in a 2012 interview that while he was a guard at Auschwitz, he was assigned to a part of the camp that was not involved in the slaughter of Jews and others.

"I didn't kill anybody, I didn't rape anybody -- and I don't even have a traffic ticket here," he said. "I didn't do anything wrong."

Breyer moved to Philadelphia after World War II and for decades lived a quiet, middle-class life with his wife, children and grandchildren. He had American citizenship because his mother was born in the U.S.; she later moved to Europe, where Breyer was born.

In 1992, the U.S. government tried to revoke Breyer's citizenship after discovering his wartime background. The effort became a yearslong legal saga and appeared to end with a 2003 decision that found Breyer had joined the SS as a minor and could therefore not be held legally responsible for participation in it.

Then he was arrested last month based on the 2013 German warrant. Officials say the arrest was delayed for a year because of the complexity of the extradition request.

His lawyers unsuccessfully argued that Breyer should be released on bail pending the extradition hearing because of his frail health. They said he has mild dementia, heart conditions and has suffered strokes in recent years.

A judge ruled that the federal prison system was capable of caring for Breyer.

"It is particularly unfortunate that Breyer could not be brought to justice in view of the significant efforts that were invested in trying to hold him accountable for his service at the Auschwitz death camp," said Efraim Zuroff, the head Nazi hunter at the Simon Wiesenthal Center in Jerusalem.

"This hurts. This hurts the families of the victims. This hurts anyone who is interested in justice," Zuroff said.